As magnetic materials that are used in a sintered ferrite magnet, Ba ferrite, Sr ferrite, and Ca ferrite which have a hexagonal crystal structure are known. Recently, among these magnetic materials, as a magnet material for motors and the like, magnetoplumbite type (M type) Sr ferrite has been mainly employed. The M type ferrite is expressed by, for example, General Formula of AFe12O19. The Sr ferrite has Sr at an A site of the crystal structure.
To improve magnetic characteristics of the sintered Sr ferrite magnet, improvement in the magnetic characteristics is attempted by substituting parts of an A-site element and a B-site element with a rare-earth element such as La, and Co, respectively. For example, Patent Literature 1 discloses a technology of improving a residual magnetic flux density (Br) and a coercive force (HcJ) by substituting parts of the A site and the B site with a specific amount of rare-earth element and Co.
The sintered Sr ferrite magnet is typically produced by using Sr ferrite particles. As a representative use of the sintered Sr ferrite magnet, a motor and a generator may be exemplified. The sintered Sr ferrite magnet that is used in the motor and the generator is demanded to be excellent in both characteristics of the Br and HcJ in combination with a high squareness ratio. However, generally, it is known that the Br and the HcJ are in a trade-off relationship. Therefore, it has been demanded to establish a technology capable of further improving both characteristics of the Br and the HcJ.
As an index indicating the magnetic characteristics in consideration of the both characteristics of the Br and the HcJ, a calculation expression of Br(kG)+⅓HcJ (kOe) is known (for example, refer to Patent Literature 1). As the value is high, it can be said that the sintered Sr ferrite magnet is suitable for a use such as the motor and the generator in which high magnetic characteristics are demanded.